The present invention is directed, in general, to a polishing pad and, more specifically, to a polishing pad having a water-repellant film thereon, and a method of manufacture therefor.
Semiconductor devices over the last few years have dramatically reduced in size. Current semiconductor technology is focusing on sub 0.35 xcexcm devices, and more specifically, sub 0.25 xcexcm devices. To accommodate such decreasing sizes, the semiconductor manufacturing industry has had to focus on current processing techniques. One of such processing techniques that has had extreme focus thereon, is chemical mechanical polishing (CMP). CMP and its derivatives appear to be the only techniques currently available, with the ability to meet the planarity requirements of sub 0.35 xcexcm circuit technology.
The CMP process involves holding, and optionally rotating, a thin, reasonably flat, semiconductor wafer against a rotating polishing platen. Likewise, the wafer may be repositioned radially within a set range on the polishing platen, as the platen is rotated. A conventional polishing pad 100 is affixed to the polishing platen and wetted by a chemical slurry, under controlled chemical, pressure, and temperature conditions (FIG. 1). As illustrated in FIG. 1, a conventional polishing pad consists of a felt pad 120 with a polyurethane pad 140 located thereover, and connected thereto with an epoxy material 130. Located below the felt pad 120 is a pressure sensitive adhesive (PSA) 110, which connects the polishing pad 100 to the above mentioned polishing platen.
To minimize set-up time and consumable costs, the CMP assembly must be kept wet, thus having slurry deposited on it at all times. This tends to cause the slurry to run down the side of the polishing platen and come in contact with the edge of the polishing pad 100. Unfortunately, current pads, and more specifically the felt pads 120, have a tendency to absorb water/fluids when in contact with the slurry. This occurs because the edge of felt pad wickens, thus, causing the entire felt pad 120 to become water/fluid logged. When the felt pad 120 stays water/fluid logged, its performance with time is negatively impacted. Furthermore, polishing pads and other materials based of polyurethane are susceptible to attacks by acids and bases. It has been found that upon exposure to a chemical environment, the solvent wets, penetrates and swells the polyurethane matrix of the polishing pads, also impacting their performance with time.
Accordingly, what is needed in the art is a polishing pad for use in current CMP technology, that does not experience the absorption problems associated with the prior art polishing pads.
To address the above-discussed deficiencies of the prior art, the present invention provides a polishing pad. In a preferred embodiment, the polishing pad includes a base pad, such as a felt pad, having an outer surface. The polishing pad also, in the same embodiment, has a water-repellant film located on the outer surface of the base pad, which, in a preferred embodiment, provides the base pad with a water absorbency factor of less than about five percent. In another embodiment, the polishing pad has an outer surface that has an outer edge, and first and second opposing surfaces joined by the outer edge. The polishing pad, in another embodiment, has the water-repellant film located on the outer edge, and one of the first and second opposing surfaces. Located on the water-repellant film on one of the first and second opposing surfaces, in another embodiment, is a pressure sensitive adhesive.
Thus, in one aspect, the present invention provides a base pad having a water-repellant film located thereon. This unique base pad inhibits fluids, acids and bases from entering the base pad and having a negative impact on their performance.
In another aspect of the invention, the water-repellant film is located on the outer edge, and the first and second opposing surfaces. In another aspect, the water-repellant film includes polyurethane and a fluorinated polymer, wherein the fluorinated polymer may be polytetrafluoroethylene. The water-repellant film should, in another aspect, be resistive to chemical reaction with acids or bases.
In another embodiment, the polishing pad has a main pad located over one of the first and second opposing surfaces, and coupled to the base pad. In such an embodiment, the water repellant film may be located over an outer edge of the main pad. In another embodiment, the water-repellant film includes a water resistant polymer, such as polystyrene, polypropylene, or polyvinyl chloride.
Another aspect of the present invention provides a polishing apparatus. The polishing apparatus, in a preferred embodiment, includes a platen, a polishing head and the polishing pad discussed previously. Furthermore, another aspect of the invention provides a method of fabricating the polishing pad. The method includes providing a base pad having an outer edge and forming a water-repellant film on the outer edge.
In another aspect, provided is a method of manufacturing a semiconductor device. The method, in a preferred embodiment, includes: (1) forming transistors on a semiconductor wafer, (2) forming a substrate over the transistors, (3) positioning the semiconductor wafer on the polishing pad described above, (4) polishing the substrate of the semiconductor wafer with the pad, and (5) interconnecting the transistors to form an integrated circuit.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.